The last Italian emperor ?

[Robert Vermaat]

But it seems one man from the motherland occassionally reached the top up to at least the
5th century AD, judging from your learned responses.

I would guess that Italy was in fact returning to the top, precisely because it wasn't the top any more. You can see a parallel development in the imperial residences: in the fifth century, we see nearly all of them residing in Rome. Italy was becoming a world of its own, and more powerful rulers were living in Trier or Constantinople.

We do? We see the top actually leaving Rome, in fact. The richest have already left for Constantinople, and the western emperors leave for Ravenna.
Milan and Trier were more important during the 4th c., Trier losing that status early in the 5th c. though. Arles is the northernmost Imperial town of importance after that, with most pretenders and emperors turning up there. Rome itself is of course still an enormous city, but left to lesser men and women, plus of course the Church.